Move layout plugin sidebar extensions to the plugin package

Summary: Moved layout plugin sidebar extensions to the plugin package.

Reviewed By: passy

Differential Revision: D27036489

fbshipit-source-id: 5b3406e5c50ba61709d925a3c0cb07a6fd7552db

desktop/plugins/public/layout/extensions/fb-stubs/index.tsx

@@ -0,0 +1,19 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ */
+
+import type {Client, Logger, PluginClient, Element} from 'flipper';
+
+export default [] as Array<
+  (
+    client: PluginClient,
+    realClient: Client,
+    selectedNode: Element,
+    logger: Logger,
+  ) => React.ReactNode
+>;